Effect of Age on the Pharmacokinetics of Marbofloxacin Following Intravenous Administration in Calves

The aim of this study was to compare the pharmacokinetics of marbofloxacin after intravenous (IV) administration of a single dose of 10 mg/kg to calves of different ages. The study was carried on 1‐ ( n = 6), 2‐ ( n = 6), and 4‐month‐old ( n = 6) Montofon calves. Plasma concentrations of marbofloxacin were measured using HPLC, and pharmacokinetic data were calculated by non‐compartmental analysis. The elimination half‐life ( t 1/2 ʎz ), volume of distribution at steady state ( V dss ), total clearance (Cl T ), and area under the concentration‐versus time curve (AUC 0–∞ ) values of marbofloxacin in 1‐month‐old calves were 10.62 h, 1.03 L/kg, 0.08 L/h/kg, and 127.90 h*μg/mL, respectively. While the t 1/2 ʎz (from 10.62 to 3.36 h) and AUC 0–∞ (from 127.90 to 47.35 h*μg/mL) decreased in parallel with the age of the calves, Cl T (from 0.08 to 0.21 L/h/kg) increased. The V dss of marbofloxacin was higher in 1‐ and 2‐month‐old calves compared to 4‐month‐old calves. After IV administration of marbofloxacin at a dose of 10 mg/kg, an ƒAUC 0–24 /MIC 90 ratio of ≥ 125 was obtained for bacteria with MIC 90 values of ≤ 0.60, ≤ 0.39 and ≤ 0.27 μg/mL in 1‐, 2‐, and 4‐month‐old calves, respectively. These results show that the antibacterial effect of marbofloxacin, which has concentration‐dependent activity, decreases due to age‐related pharmacokinetic changes and that the 10 mg/kg dose should be reviewed according to the MIC 90 value of the bacteria.